This invention relates to means for metering particular material and is particularly, but not exclusively, concerned with means for metering agricultural seed and/or fertilizer from the hopper of a seed and fertilizer drilling apparatus.
Agricultural seed and fertilizer drilling apparatus is known which comprises a hopper mounted on a wheeled support and wherein the floor of this hopper defines an exit which is closed by a pair of contrarotatable rollers each of which is covered with a layer of compressible foraminous material providing a nip therebetween through which the seed and/or fertilizer may be discharged from the hopper at a controlled rate. Apparatus of this kind, however, may have certain disadvantages in use. Thus, for example, the rollers may be subject to shrinkage or wear in use and this can lead to variability of throughput over a period of use. In order to compensate for this shrinkage and/or wear of the rollers, a complicated mechanism of roller adjustment is required.